Effect of Temperature and Galvanization on Cold-Formed Steel

An experimental program was conducted to study the effect of temperature and galvanization on the mechanical properties of cold-formed steel members typically used in constructing hydroelectric transmission towers. Two types of steel were used in this program, ASTM A715 Grade 60 and CSA G40.21-300W. A series of 144 tension coupons was cut from steel members type ASTM A715 Grade 60 and another series of 48 tension coupons was cut from steel members type CSA G40.21-300W. Coupons cut from both ungalvanized and galvanized members were tested according to ASTM standards at temperatures ranging from −50°C to room temperature. In addition, semiguided bend tests were performed to check the ductility of the materials, and Charpy V-notch impact tests were conducted to study the effect of low temperature on toughness. The test results showed that the processes of hot-dip galvanizing and cold forming, coupled with low temperatures resulted in an increase of the yield and ultimate strengths, as well as in the modulus of elasticity of the materials. These processes, however, resulted in a reduction of their ductility. The degree to which these processes affected the mechanical properties depended on the type of steel. The mechanical properties of the CSA G40.21-300W steel were affected a lot more by these processes than were those of ASTM A715 Grade 60 steel.